How do I replicate one value based on a previous value?
e.g
My dataset
name <- c("sergio",NA,NA,NA,NA,"John", NA,NA,NA,NA,NA,NA) number <-c(1234,NA,NA,NA,NA,5678, NA,NA,NA,NA,NA,NA) mydata <- cbind(as.data.frame(name),as.data.frame(number)) New dataset
name number sergio 1234 sergio 1234 sergio 1234 sergio 1234 John 5678 John 5678 John 5678 John 5678 John 5678 John 5678 .... etc
You can use na.locf from the "zoo" package:
mydata <- data.frame( name = c("sergio",NA,NA,NA,NA,"John", NA,NA,NA,NA,NA,NA), number = c(1234,NA,NA,NA,NA,5678, NA,NA,NA,NA,NA,NA)) library(zoo) na.locf(mydata) # name number # 1 sergio 1234 # 2 sergio 1234 # 3 sergio 1234 # 4 sergio 1234 # 5 sergio 1234 # 6 John 5678 # 7 John 5678 # 8 John 5678 # 9 John 5678 # 10 John 5678 # 11 John 5678 # 12 John 5678 If you prefer to not use a package, here's something that might work:
LOCF <- function(x) { A <- cumsum(!is.na(x)) ave(x, A, FUN = function(x) x[1]) } mydata[] <- lapply(mydata, LOCF) 
You can also use a simple home-brewed function:
copydown <- function(x) { for(iii in seq_along(x)[-1]) if(is.na(x[iii])) x[iii]<- x[iii-1] x } > copydown(name) # [1] "sergio" "sergio" "sergio" "sergio" "sergio" "John" "John" "John" # [9] "John" "John" "John" "John" mydata[] <- lapply(mydata, copydown) # notice [] -- so the result will be a data frame rather than a list 